The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Coming Off Mounjaro: Side Effects and What to Expect
Stopping Mounjaro (tirzepatide) can trigger specific side effects and changes in your body that many people don't anticipate. This guide explains what happens when you come off this prescription weight loss injection, how it compares to stopping Wegovy, and why medical supervision matters. Whether you're discontinuing for medical reasons or considering a switch, understanding the process helps you prepare. Use our free GLP-1 weight loss calculator to understand your current treatment context before making any changes.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Understanding Mounjaro Withdrawal and Rebound Effects
When you stop taking Mounjaro, your body doesn't immediately return to baseline. Unlike some medications, there is no formal "withdrawal syndrome," but rebound effects are common and well-documented:
- Return of appetite — typically within days to weeks as GIP and GLP-1 signalling decreases
- Rebound weight gain — research suggests most people regain 50–100% of lost weight within 1–2 years if lifestyle changes aren't maintained
- Blood sugar changes — if you have type 2 diabetes or prediabetes, glucose control may worsen
- Nausea and digestive changes — paradoxically, some people experience nausea for 1–2 weeks after stopping, though this is less common
- Fatigue and mood changes — some users report temporary low energy or mood dips
These effects are not dangerous but can be uncomfortable. The key to managing them is maintaining the dietary and lifestyle changes you've made during treatment. Our BMI calculator can help you track where you stand in relation to healthy weight ranges as you navigate this transition.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mounjaro vs Wegovy: Stopping and Side Effects Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) work via GLP-1 pathways, so stopping either produces similar rebound effects — but with important nuances. Mounjaro's dual GIP+GLP-1 mechanism means some users experience slightly more pronounced appetite rebound when stopping, as both pathways reset simultaneously. Wegovy's single GLP-1 mechanism typically results in equally significant rebound, though the timeline may be slightly more gradual. Clinical trial data shows no meaningful difference in weight regain between the two. Individual experience varies based on your Mounjaro dose titration level and how long you've been on treatment. Neither medication is "easier" to stop — both require a prescriber's guidance and a solid maintenance plan. Your GP or prescriber can advise whether switching to Wegovy or another approach suits your situation better.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
What's the difference between Mounjaro withdrawal and Wegovy withdrawal?
Both cause similar rebound appetite and weight regain because they work through GLP-1 pathways. Mounjaro's additional GIP mechanism may cause slightly more pronounced appetite return, but clinical outcomes are comparable. Stopping either requires a prescriber's guidance and lifestyle maintenance to prevent full weight regain.
How quickly does appetite return after stopping Mounjaro?
Most people notice appetite returning within 3–7 days of stopping. Full appetite normalisation typically occurs within 2–4 weeks. This is not dangerous but can feel sudden and uncomfortable, which is why gradual dose reduction under prescriber supervision is often recommended rather than stopping abruptly.
Will I regain all the weight I lost on Mounjaro?
Research suggests most people regain 50–100% of weight within 1–2 years after stopping if lifestyle changes aren't maintained. However, many people keep some weight off long-term by maintaining diet and exercise habits learned during treatment. Your GP can help you plan a sustainable maintenance strategy.
Is it better to switch from Mounjaro to Wegovy or stop completely?
This depends on your individual health, eligibility, and prescriber's assessment. Some people switch if Mounjaro hasn't been effective or side effects are problematic. Others benefit from stopping and maintaining lifestyle changes. Your prescriber will assess whether switching suits your UK eligibility and health needs.
Can I stop Mounjaro suddenly or should I taper the dose?
Stopping suddenly is not medically dangerous, but tapering (gradually reducing dose over 4–8 weeks) under your prescriber's guidance can ease appetite rebound. Your GP or Mounjaro prescriber can advise on the best approach for your situation, especially if you're on a high maintenance dose like 15 mg weekly.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.